This invention relates to a grounded support tank type gas circuit breaker comprising a breaking unit disposed within a grounded tank in electrically insulated relation from the tank. More particularly, this invention relates to the arrangement of a capacitor used in conjunction with a circuit breaker of the type above described.
The progressively increasing power demand calls for power transmission lines of larger capacity capable of transmission of higher voltage. Circuit breakers used for the protection of electrical equipments connected to such high-voltage transmission lines are also required to possess a larger capacity capable of breaking high-voltage circuits. A circuit breaker used with such a high-voltage transmission line of increased transmission capacity is required to reliably break the circuit even in such a severe condition as occurrence of a short line fault. An excessively high transient recovery voltage is applied across the contacts of the circuit breaker during interruption of the current flowing through the circuit due to the short line fault. It is commonly known that suppression of the initial rate of rise of the recovery voltage applied across the contacts of the circuit breaker is one of the effective means for improving the breaking capability of the circuit breaker in dealing with the short line fault. As a practical example, such means comprises a capacitor connected between the ground and the line side conductor of the circuit breaker.
A potential divider is required for the purpose of voltage measurement in a substation in which a circuit breaker is disposed. This potential divider is generally disposed independently of the circuit breaker and comprises a primary capacitor connected at one terminal thereof to the line side conductor of the circuit breaker.
As pointed out above, a plurality of capacitors are disposed in the vicinity of a circuit breaker in a substation to make various individual services, and since these capacitors are independent of each other, a plurality of independent support means or containers, for the capacitors are required in the substation. Further, independent spaces are required for the installation of these capacitors.
A grounded support tank type gas circuit breaker is known in the art. This known circuit breaker comprises, within a grounded support tank, a capacitor which is capable of controlling the initial rate of rise of recovery voltage. However, this known grounded support tank type gas circuit breaker has been such that the capacitor is merely disposed within the grounded support tank and is not necessarily located at a most desirable position in the circuit breaker from the structural and operational point of view. More precisely, the capacitor used heretofore for limiting the initial rate of rise of recovery voltage has been disposed in a dead space of the grounded support tank. It has therefore been difficult to find a space for the installation of this capacitor in a grounded tank of a gas circuit breaker of this type which is designed ideally so as not to leave any dead space within the grounded support tank. Thus, an attempt to incorporate this capacitor in the ideal circuit breaker has resulted in the necessity for renewing the design of the grounded support tank.